1. Field of the Invention
The present invention relates generally to packaging processes, and, more particularly, to a process for the removal of packaging material from heat-sensitive food products. Specifically, the preferred embodiment of this invention relates to a process wherein sausage casings are split from end-to-end with a laser beam to allow ready removal of the casing without accompanying surface damage to the sausage.
2. Description of the Prior Art
In the past, sausage products were commercially prepared by stuffing or blowing a meat emulsion into a carbon-based casing. The casing retained the sausage shape during cooking. The casing material, which most often was cellulose, was removed from the sausage after the cooking process to produce a fully edible product. The removal was usually accomplished by cutting or splitting the casing along the length of the sausage with a knife, and then mechanically stripping the casing away from the meat. It the cutting blade was not precisely adjusted, the sausage was also cut, leaving unsightly and undesirable marks on the meat surface. Frequent replacement of the knife blade and adjustment of the cut depth were regarded in the industry as necessary expenses. A need existed for a method of consistently splitting sausage casings without damaging the contained sausage product.
A particularly good example of the problems encountered when cutting a casing with a knife or razor was to be found in the manufacture of some hot dogs. A meat emulsion was prepared and blown into a cellulose casing material. The hot dogs were then formed into the well-known, rounded-end cylindrical shape using a "linker" which produced a connected "string" of the sausages. The strings of hot dogs were hung on a "stick" and passed through an oven where they were cooked. Following cooking, the cellulose casing was removed or "peeled" from each hot dog by feeding the string of hot dogs through a peeler. The peeler had a cutting blade appropriately mounted so as to slice each casing as the hot dog passed longitudinally beneath the blade. When the cutting blade was precisely adjusted, the resulting cut did not extend to the portions of the casing covering the rounded ends of the sausages. As each hot dog exited the peeler, a mechanical device pulled the continuous casing away from the hot dogs, leaving the hot dogs ready for display packaging. The casing removal operation required that the casing be continuously split across the length of the hot dog. When the string of hot dogs was fed through the peeler at high speed, the hot dogs bounced as they passed below the knife. Peeler cuts resulted in some areas, while other areas of the casing remained uncut. When the uncut portions of the casings were substantial, the casing removal device often malfunctioned and resulted in a string of the hot dogs passing through the peeler with the casings partially split but still in place. The subsequent manual removal of the casings was inordinately expensive. A need existed for a method of consistently splitting hot dog casings from end-to-end without damaging the hot dogs notwithstanding size, shape or movement peculiarities of individual hot dogs.
Since contamination of the sausage product was an ever-present danger, a need existed for a casing removal method which minimized or eliminated contact of a blade with the sausage.
As evidenced by U.S. Pat. No. 2,627,466, an attempt had been made some 30 years ago to solve the problem of peeler cuts on hot dogs. The method there disclosed utilized a soluble casing material, which was at least partially dissolved from the hot dog during or after the cooking process. While peeler cuts were avoided, that process presented other problems, including the relatively greater cost of the casing material and the requirement that the hot dogs be washed and dried prior to packaging. A need continued to exist for a method to mechanically remove conventional cellulose-based hot dog or sausage casings.
Many diverse uses for lasers have been developed in recent years, including hole drilling, welding, material removal, cutting, scribing, sealing and trimming of a variety of organic and inorganic materials. The lasers which have received the most attention to date are the ruby, neodymium-doped glass, neodymium-doped yttrium aluminum garnet and carbon dioxide types, although many others are also amenable to such applications. Certain applications, such as hole drilling, preferably utilize pulsed lasers, whereas other applications, for example welding and cutting, are best accomplished with continuous wave lasers.
The projection or focusing of a laser beam onto an absorbtive body resulted in transformation of the radiant energy into heat energy. Thus, as illustrated by French Pat. No. 2,305,936, the expected application of a laser to a heat-sensitive food product would be for cutting or slicing through the product by thermally vaporizing a path through the product. That patent gives rise to an expectation that the projection of a laser beam onto a protein-based product such as a hot dog would result in at least a de-naturing of irradiated protein molecules. A need continued to exist for an apparatus or process to provide automated removal of a casing from a heat-sensitive food product without slicing into, slicing through, or otherwise degrading the product.